1. Field of the Invention
This invention relates generally to reverse buckling rupture disk apparatus, and more particularly, but not by way of limitation to improved reverse buckling rupture disk apparatus adapted to be clamped between companion bolted flanges and methods of manufacturing such apparatus.
2. Description of the Prior Art
Reverse buckling rupture disk apparatus have been developed and utilized heretofore. Such apparatus generally include a reverse buckling rupture disk having a concave-convex portion connected to an annular flange portion by a transition connection. In most of the prior apparatus, the annular flange portion of the rupture disk is clamped between inlet and outlet support members which are in turn adapted to be clamped between companion bolted flanges. Knife means for severing the rupture disk upon the reversal thereof are attached to the outlet support member or otherwise held in the apparatus. Various other arrangements have also been developed and used whereby one or both of the support members are omitted and/or other structure is substituted therefor.
In all of such prior apparatus wherein the annular flange portion of the reverse buckling rupture disk is clamped between companion bolted flanges with or without support members or other structure therebetween whereby the clamping pressure of the flanges is transmitted to the flange portion of the rupture disk, the operation of the rupture disk is adversely affected by changes or differences in the torque applied to the flange bolts. That is, changes or differences in the clamping pressure exerted on the rupture disk produce changes in stresses in the disk, particularly in the area of the transition connection, whereby the fluid pressure required to cause the disk to reverse and rupture is altered. Thus, when such a reverse buckling rupture disk apparatus is clamped between companion flanges, if too much or too little torque is applied to the flange bolts, the fluid pressure level at which the rupture disk fails can be changed appreciably from the predetermined design rupture fluid pressure level. This, in turn, can result in premature failure of the rupture disk or the existence of an overpressure condition in the vessel or system being protected without failure of the rupture disk.
In order to overcome or reduce changes in rupture pressure due to overtorquing or undertorquing the flange bolts, such reverse buckling rupture disk apparatus have been preassembled at the factory whereby the proper torque is applied to the rupture disk. In cases where the apparatus cannot be preassembled, precise instructions relating to the proper amount of torque to be applied to the flange bolts have been furnished to users of the apparatus. While these procedures have been effective to some extent, once a reverse buckling rupture disk apparatus has been installed, the disk cannot be removed for inspection purposes and reinstalled without inducing new stresses in the disk which alter its operational characteristics. Consequently, it has been the practice in the industry that once a reverse buckling rupture disk has been clamped between support members and/or flanges and removed, it is discarded and replaced.
By the present invention an improved reverse buckling rupture disk apparatus is provided which is adapted to be clamped between companion bolted flanges, the operation of which is unaffected by changes or differences in the torque applied to the flange bolts.